Crystallographic methods will be used for investigating the structure of crystalline amino acids, proteins, and viruses. Electron scattering data will be analyzed both in the form of direct diffraction intensities and in the form of Fourier transforms of electron micrographs. Quantitative interpretation of these data will be refined, and precision of structural parameters will be improved, by taking into account the theoretical corrections that are associated with multiple electron scattering (dynamical scattering). BIBLIOGRAPHIC REFERENCES: R.M. Glaeser and Bing K. Jap, Dynamical Scattering in Crystalline Biological Specimens. I. Criteria of Validity for Scattering Approximations, 33rd Ann. Proc. Electron Microscopy Soc. Amer., Las Vegas, Nevada, 1975. G.W. Bailey (ed.) Bing K. Jap and Robert M. Glaeser, Dynamical Scattering in Crystalline Biological Specimens. II. The Domain of Validity for Different Approximation, 33rd Ann. Proc. Electron Microscopy Soc. Amer., Las Vegas, Nevada, 1975. G.W. Bailey (ed).